Plate carrier

ABSTRACT

A plate carrier for a multi-plate clutch comprises: an annular member with a first circumferential face and a second circumferential face; a toothing in the first circumferential face of the annular member, having circumferentially distributed teeth and gaps; at least one groove in the second circumferential face of the annular member, wherein the groove extends over a circumferential portion of the annular member, wherein the groove and the toothing intersect one another, so that radial apertures are formed in the regions of intersection between the groove and the tooth gaps. A multi-plate clutch can be provided with such a plate carrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims the benefit of priorityto, co-pending U.S. patent application Ser. No. 14/520,570, filed onOct. 22, 2014, which claims priority to German Patent Application No. 102013 111 877.1 filed on Oct. 28, 2013, each of which prior applicationsare hereby incorporated herein by reference in their entireties.

BACKGROUND

From DE 10 2011 102 748 A1, a double clutch is known for a dual clutchtransmission of a motor vehicle. The double clutch comprises twoclutches each having an outer plate carrier, an inner plate carrier anda plate package. In the plate carrying region, the inner plate carriercomprises a plurality of cooling fluid apertures which extend from theinner circumferential face to the outer circumferential face. Thecooling fluid apertures each end between the teeth of the inner platecarrier and are arranged so as to be axially and circumferentiallyoffset relative to the adjoining cooling fluid apertures. At the innercircumferential face there is provided a cooling fluid guiding elementin the form of an annular oil guiding plate. The oil guiding platecomprises a plurality of oblong slots which are separated from oneanother by transverse webs. The slots are each arranged in the region ofthe cooling fluid aperture.

From DE 10 2007 055 151 A1, corresponding to US 2008/0142330 A1, thereis known a double multi-plate clutch for the transmission of torquebetween a brake force generator and a multi-step transmission. Thedouble multi-plate clutch comprises an outer multi-plate clutch and aninner multi-plate clutch. The outer plate carrier of the outermulti-plate clutch and the outer plate carrier of the inner multi-plateclutch each comprise a toothed member which is produced by roll forming.The toothed members are formed in such a way that, on the radial inside,they comprise inner teeth and, on the radial outside, they compriseouter teeth. The outer teeth each comprise apertures.

Document EP 1 422 430 A1, corresponding to US 7 007 783 B2, alsoproposes a double multi-plate clutch. An outer plate carrier of theclutch is provided in the form of a pressed and punched plate componentand comprises a base and a cylindrical portion. The cylindrical portion,on its radial inside, comprises circumferentially distributedalternating axial grooves and axial webs. The axial grooves are providedfor the purpose of ensuring a rotationally fixed engagement of the outerplates and comprises centrally positioned apertures to allow the radialthrough-flow of hydraulic oil.

From DE 10 2006 031 786 A1, corresponding to US 8 061 497 B2, amulti-plate clutch or multi-plate brake is known which comprises aninner plate carrier with inner plates and an outer plate carrier withouter plates. The inner plate carrier and, respectively, the outer platecarrier are formed of a plurality of parts and comprise a base part anda toothed part which embraces the latter and to which the plates areconnected in a rotationally fixed way. The base part and the toothedpart are provided with radial apertures which are fluidly connected toone another to allow a through-flow.

SUMMARY

Disclosed herein is a plate carrier for a friction plate clutch, theplate carrier for use in the driveline of a motor vehicle. Alsodisclosed is a friction plate clutch having such a plate carrier. Thefriction plate clutch is suitable for transmitting torque between aclutch input part and a clutch output part or, optionally, forinterrupting a transmission of torque.

The plate carrier for a multi-plate clutch promotes good cooling of theclutch in the actuated condition, and good de-oiling in the non-actuatedcondition, to thereby minimize drag torque. The plate carrier compriseshigh static and dynamic strength values and can be produced easily andcost-effectively. Furthermore, a multi-plate clutch having such a platecarrier, while comprising high strength values, is provided with goodcooling properties and low drag moments in an open condition. Inaddition, a simple and cost-effective process of producing such a platecarrier with said properties is disclosed.

Accordingly, a plate carrier for a multi-plate clutch may comprise: anannular member with a first circumferential face and a secondcircumferential face; a toothing in the first circumferential face ofthe annular member, having teeth and tooth gaps circumferentiallydistributed; at least one groove in the second circumferential face ofthe annular member, wherein the groove extends at least over acircumferential portion of the annular member; wherein the groove andthe toothing intersect one another such that along a circumferentialextension of the groove radial several apertures are formed in theannular member in regions of intersection between the groove and thetooth gaps.

An advantage is that the plate carrier ensures a good through-flow ofcoolant through the multi-plate clutch which can flow through theapertures distributed over the circumference. The plate carrier can beprovided in the form of an outer plate carrier, with the teeth thenbeing provided at the inner circumferential face, with the groove beingarranged at an outer circumferential face; or the plate carrier can beprovided in the form of an inner plate carrier, with the teeth,accordingly, being provided at an outer circumferential face and thegroove being provided at the inner circumferential face. Acircumferential face in this regard can be an outer face and,respectively, an inner face of the plate carrier, which respective faceextends in the circumferential direction. More particularly, the firstand/or the second circumferential face can be cylindrical and, to thatextent, can also be referred to as cylindrical faces.

A particular advantage of the plate carrier being provided in the formof an outer plate carrier is that the cooling agent, when the clutch isopen, can escape easily and quickly out of the plate package radiallyoutwardly through the apertures. Thus, a reduction in any drag momentswhich are caused by relative rotational movement between the outerplates and the inner plates can be achieved.

In addition to the excellent flow characteristics of the coolant,another advantage is achieved in that the plate carrier features highstatic and dynamic strength values combined with easy and cost-effectiveproduction conditions. By producing a groove in the circumferential faceradially opposite the toothing, a plurality of apertures can be producedin one production stage. There is no need for boring or punching outindividual apertures. The coolant refers to any substance that can beused for cooling the multi-plate clutch or parts thereof, such ascooling lubricant or oil.

The groove extends in a circumferential direction along an inner orouter circumferential face of the annular member, e.g., at least along acircumferential section of the annular member which comprises severaltooth gaps. The tooth gaps refer to the spaces between each twocircumferentially adjacent teeth, and can thus also be referred to astooth spaces. As already mentioned, the plate carrier can be provided inthe form of an outer plate carrier according to a first possibility, inwhich case the second circumferential face constitutes an outer face ofthe annular member, with the first circumferential face constituting aninner face of the annular member, wherein a smallest radius of thegroove base is smaller than a largest tooth base radius of the teeth.According to a second possibility, the plate carrier can be provided inthe form of an inner plate carrier, with the second circumferential faceconstituting an inner face of the annular member and the firstcircumferential face constituting an outer face of the annular member,wherein, furthermore, a greatest radius of the groove base is greaterthan a smallest tooth base radius of the teeth. Unless otherwise stated,all of the below-mentioned embodiments apply to both possibilities.

More particularly, the groove, starting from the second circumferentialface, comprises a groove depth, and the tooth gaps starting from thefirst circumferential face comprise a tooth gap depth in across-sectional plane axially adjoining the groove, wherein the sum ofgroove depth and tooth space depth is greater than the radial thicknessbetween the first circumferential face and the second circumferentialface. Thus, it is possible to achieve a geometric overlap between thegroove and the teeth, thereby ensuring a reliable production of theapertures with a defined geometry. In this regard, geometric overlappingmeans that the toothing defines an imaginary first hollow space, andthat the groove defines an imaginary second hollow space, wherein thefirst and second hollow spaces, in an axial view, comprise regions ofintersection which form the radial apertures. The first and secondhollow spaces may also be referred to as cavities.

In principle, the at least one groove can be provided in any number andin any form which can be adapted to the requirements regarding strengthand through-flow capacity of the plate carrier. To achieve a highthrough-flow capacity, a large through-flow surface can be provided byusing several grooves which, more particularly, can be distributed overthe axial length of the plate carrier. If high strength values are moreimportant, it is possible to use several grooves in one circumferentialplane which are separated from one another by a reinforcing web.

For example, one or more of the following embodiments are conceivable:it is possible to provide only one groove which at least substantiallyextends in the circumferential direction. The groove can thus also bereferred to as a circumferential groove. The expression “at leastsubstantially in the circumferential direction” as used herein includesthe possibility of the groove being positioned in a plane extendingperpendicularly relative to the longitudinal axis of the plate carrieror of the groove comprising at least one portion which, relative to aperpendicular plane, comprises a gradient component in an axialdirection, i.e. is shaped slightly helically. The gradient angle betweenthe groove and a plane extending perpendicularly relative to thelongitudinal direction can, more particularly, be smaller than or equalto 20°. It applies to both possibilities, i.e. a groove without or withan axial gradient, that the groove can be circumferentially finite orthat it can be continuously closed, i.e., provided in the form of anannular groove. In the embodiment comprising a finite groove, it ispossible that several grooves are arranged so as to be circumferentiallydistributed, for instance, two, three or four grooves, with a separatingweb being formed between each two circumferentially adjoining grooves.According to a further embodiment, a plurality of grooves can bearranged along the width (axial length) of the plate carrier which canbe arranged so as to be axially spaced from one another. Each of thegrooves thus forms a row of apertures in the region of intersection withthe tooth gaps between the teeth. The grooves can each be positioned ina radial plane or they can circumferentially extend slightly helicallywith an axial gradient component relative to the longitudinal axis ofthe plate carrier. For good oil flow characteristics it is advantageousif each two adjoining helical grooves circumferentially overlap oneanother at least with partial portions. It can apply to all embodimentsthat the at least one groove, in a cross-sectional view, comprisesrounded recesses, which reduces stresses in the component, which thusleads to a high strength value and an increase in service life.

The geometry of the apertures is largely determined by the geometry ofthe teeth, respectively toothing. In the circumferential direction, theradial apertures are delimited by two opposed side faces of twoadjoining teeth. In the regions laterally or axially adjoining thegroove, the gaps occurring between two adjoining teeth form channelsthrough which clutch oil is able to flow axially to the respectiveaperture. To achieve a good flow behaviour it is advantageous if theteeth, in a base region, each comprise a substantially constantthickness. This shall also include that the tooth flanks in this baseregion extend between a radial plane and a parallel plane with referenceto the longitudinal axis. More particularly, the tooth flanks of twoopposed teeth in the base region can extend substantially parallelrelative to one another.

In a cross-sectional plane through the groove, the teeth comprise agreatest tooth thickness, and the apertures between two teeth comprise agreatest width, with the ratio between tooth thickness and widthamounting to at least one and/or a maximum of three. This embodimentachieves a particularly high strength value of the plate carrier. Thetooth thickness and the width of the apertures each refer to thecircumferential direction of the plate carrier. The expression“cross-sectional plane through the groove” refers to a section throughthe groove base along the circumferential extension of the groove.

Furthermore, in a cross-sectional plane through the groove, the teethcomprise a greatest tooth height, and the annular web between the secondcircumferential face and the tooth base lines of the toothing comprisesa radial thickness, wherein the ratio between the tooth height and theradial thickness of the annular web preferably amounts to one and/or amaximum of two. This embodiment, too, advantageously contributes to ahigh strength value of the plate carrier.

The ratio between a greatest outer diameter of the annular member andthe radial thickness of the annular web between the secondcircumferential face and the tooth base lines of the toothing can besubject at least to one of the following: the greatest outer diameter ofthe annular member corresponds to at least 35 times, or at least 55times the radial thickness of the annular web; and/or the greatest outerdiameter of the annular member corresponds to maximal 95 times, ormaximal 75 times the radial thickness of the annular web. In this way,good strength properties of the plate carrier can be achieved.

The plate carrier can be configured such that in longitudinal sectionsthrough the plate carrier one or more apertures are provided, whereinthe sum of all apertures existing in a longitudinal section define acumulated length, wherein the ratio of the cumulated length of the atleast one aperture to the effective axial length of the teeth ispossibly at least 0.2 and/or a maximum of 0.6. Thus, a good compromisebetween the achievable quantity of oil through-flow and the strength ofthe plate carrier can be achieved. In this context, effective lengthrefers to the length along which the plate package extends in thebuilt-in condition and, respectively, the length along which atransmission of torque takes place. The effective length of the teeth isshorter than the total length of the plate carrier.

Furthermore, a multi-plate clutch can comprise a first plate carrier towhich the first plates are connected in a rotationally fixed and axiallymovable way; a second plate carrier to which second plates are connectedin a rotationally fixed and axially movable way; wherein the first platecarrier and the second plate carrier are rotatable relative to oneanother around an axis of rotation, wherein, by introducing an axialforce, the first plates and the second plates are brought into frictioncontact with one another for selectively transmitting torque between thefirst plate carrier and the second plate carrier, wherein at least oneof the first and second plate carriers is configured according to atleast one of the above-mentioned embodiments.

The multi-plate clutch offers the same advantages of good through-flowconditions for the clutch and simultaneously high strength which havealready been mentioned in connection with the presently disclosedmulti-plate carrier. For reducing the drag torque of the clutch, it isadvantageous if the outer one of the first and the second platecarrier—which can also be referred to as the outer plate carrier—isconfigured in said design with a groove. In this embodiment, theoutwardly flowing cooling agent can escape from the plate packetparticularly rapidly, when the clutch is open, which leads to areduction in the drag moment.

However, also the embodiment of the inner plate carrier in said designhas advantages, i.e., in respect of an effective cooling system for theplate package. Due to the large number of apertures it is possible for arelatively large quantity of cooling agent to reach the plate packagefrom the radial inside for the purpose of cooling the plates. Inaddition, because of the great strength of the at least one platecarrier, the clutch is able to transmit a particularly high torque.

Furthermore, the objective of the invention is achieved by a process ofproducing a plate carrier for a multi-plate clutch with the followingprocess stages: providing an annular member with a longitudinal axis anda toothing in a first circumferential face of the annular member,wherein teeth and tooth gaps of the toothing extend in the axialdirection; working a groove into a second circumferential face of theannular member, which groove at least substantially extends in thecircumferential direction; wherein the groove, starting from the secondcircumferential face, is worked sufficiently deeply into the annularmember such that along a circumferential extension of the groove severalradial apertures are formed in the annular member in intersectingregions between the groove and the tooth gaps.

In an advantageous way, said process allows several apertures to beproduced simultaneously in one working operation. A further advantageconsists in that the process, is suitable for producing plate carriersout of a solid component as a starting part. In this regard, solidcomponents, for example, are parts which can be produced by solidforming or chip-forming machining or a powder metal process. Thisembodiment ensures great plate carrier strength allowing thetransmission of high torque values. It is understood that any embodimentof the process is applicable to the product, and vice versa.

According to a first possibility, the processes of producing the annularmember and working in the teeth are carried out in one operation in thatthe annular member is pressed out of powder metal and solidified in asintering process. Subsequently, the groove can be worked into thesintered component, preferably by a chip-forming operation such asturning or milling. Producing the plate carrier by sintering ensuresparticularly high production accuracies of the carrier toothing, whichhas an advantageous effect on the carrying capacity in respect of theplate toothing of the plates to be form-fittingly received. Sintering isparticularly suitable for medium-sized quantities where the toolingcosts are relatively low. In the case of large quantities, theproduction of formed plate metal parts may also be suitable. To thatextent, there exists a second possibility in that the plate carrier isproduced by forming same out of a plate metal part where, initially aplate metal strip is formed into a sleeve with inner and outer teeth.The apertures are worked in subsequently, which can be done bychip-forming machining such as turning or milling.

DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be explained below with reference to thedrawings wherein

FIG. 1 shows an exemplary plate carrier in a first embodiment in alongitudinal section, in the form of an outer plate carrier.

FIG. 2 shows the plate carrier according to FIG. 1 in athree-dimensional view.

FIG. 3 shows the annular portion of the plate carrier according to FIGS.1 and 2 in a three-dimensional view.

FIG. 4 is a longitudinal section through the annular portion accordingto FIG. 3.

FIG. 5 is a radial view of the annular portion according to FIG. 3.

FIG. 6 shows a detail of the annular portion according to FIG. 3 in anaxial view.

FIG. 7 shows a detail of the annular portion according to FIG. 3 in alongitudinal section along sectional line VII-VII of FIG. 6.

FIG. 8 shows an exemplary plate carrier in a second embodiment in aradial view, in the form of an outer plate carrier.

FIG. 9 shows an exemplary plate carrier in a third embodiment in aradial view, in the form of an outer plate carrier.

FIG. 10 shows an annular portion of an exemplary plate carrier in afourth embodiment in a three-dimensional view, in the form of an outerplate carrier.

FIG. 11 is an axial view of the annular portion according to FIG. 10.

FIG. 12 shows an exemplary plate carrier in a further embodiment in athree-dimensional view, in the form of an outer plate carrier.

FIG. 13 shows the annular portion of an exemplary plate carrier in afurther embodiment in a three-dimensional view.

FIG. 14 shows the annular portion according to FIG. 13 in across-sectional view through the groove.

FIG. 15 shows an exemplary plate carrier in a further embodiment in aradial view, in the form of an inner plate carrier.

FIG. 16 is a longitudinal section through the plate carrier according toFIG. 15, and

FIG. 17 shows the plate carrier of FIG. 15 in a cross-sectional viewalong sectional line XVII-XVII of FIG. 16.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 7 will be described jointly below. There is shown a platecarrier 2 for a friction plate clutch in a first embodiment. A frictionplate clutch generally comprises two plate carriers which are rotatablerelative to one another around an axis of rotation, i.e. an outer platecarrier in which outer plates are received in a rotationally fixed andaxially movable way, and an inner plate carrier at which inner platesare held in a rotationally fixed and axially movable way. The outerplates and the inner plates are arranged so as to alternate axiallyrelative to one another and jointly form a plate package. A frictionplate clutch can also be referred to as multi plate clutch or multi discclutch.

The plate carrier 2 shown in FIGS. 1 to 7 is provided in the form of anouter plate carrier which comprises a hub portion 3 with hub teeth 4which can be made to engage a driveshaft (not illustrated) withcorresponding shaft teeth for transmitting torque. Furthermore, theplate carrier 2 comprises a flange portion 5 which extends radiallyoutwardly from the hub portion 3, as well as an annular portion 6 whichis connected to the flange portion 5 and which is arranged coaxially tothe hub portion 3. The annular portion 6 extends in axial direction andmay also be referred to as annular member, casing portion or cylindricalportion.

The annular member 6 comprises a first circumferential face 7 whichforms an inner circumferential face of the annular member 6, as well asa second circumferential face 8 which forms an outer circumferentialface.

Radially in an interior, the annular member 6 comprises a toothing 9 inthe form of an inner toothing which is engaged in a rotationally fixedand axially movable way by a corresponding outer toothing of outerplates 10 for transmitting torque. The outer plates 10 are shown inFIG. 1. It can be seen that the plates 10 are arranged so as to beaxially spaced from one another. These gaps are engaged by inner plates(not shown) of an inner plate carrier of the friction clutch. The outerplate carrier 10 and the inner plate carrier jointly form the platepackage. The plate package is axially supported against a supportingface 26 of the flange portion 5 and can be loaded with an axial force bya pressure plate 11, so that a friction contact between the outer plates10 and the inner plates is achieved, with torque being transmittedbetween the outer place carrier 2 and the inner plate carrier. Thepressure plate 11 can be loaded by an actuator shown) which can beprovided fo,r example, in the form of an electro-magnetic,electro-mechanical or hydraulic actuator.

The toothing 9 comprises circumferentially alternating teeth 11 andtooth gaps 12 which extend in the axial direction. In the presentembodiment, the teeth 11 extend parallel to the longitudinal axis A,i.e., the toothing 9 comprises straight teeth. However, it is understoodthat the teeth can also be slightly inclined, i.e., provided in the formof helical teeth. The teeth 11 comprise a tooth head line 13 which canalso be referred to as addendum line, addendum circle or tip circle. Theradially inner face which defines the tip circle forms the inner firstcircumferential face 8 of the annular member 6.

A groove 14 is provided in the second circumferential face 7,respectively worked into said second face. The groove 14 extends in thecircumferential direction. In the present embodiment, the groove 14 iscontinuously closed and, in that respect, can also be referred to as anannular groove. The annular groove 14 extends in a plane which extendsperpendicularly relative to the longitudinal axis A and divides theouter circumferential face 7 into two axially spaced surface portions.With reference to the axial length of the plate package, the annulargroove 14 is arranged approximately centrally, which is particularlyobvious in FIG. 1. The groove 14 extends from the outer circumferentialface 7 radially inwardly as far as and beyond a tooth baseline 15 of thetoothing 9, so that in the region of the circumferential extension ofthe groove 14, between each two teeth 11, there are formed radialapertures 16. The tooth baseline 15 can also be referred to as rootline, root circle or addendum circle.

It can be seen in FIG. 6, which shows part of the annular member 6 in anaxial view in the form of an enlarged detail, that, starting from theinner circumferential face 7, the tooth gaps 12 comprise a gap depth H9which corresponds to the tooth height. The gap height H9 extends betweena tooth tip radius R11 and a tooth base radius R12. Furthermore,starting from the outer circumferential face 8, the groove 14 comprisesa groove depth H14. Furthermore, between the inner circumferential face7 and the outer circumferential face 8, the annular member 6 comprises aradial extension H6 which can also be referred to as thickness. It canbe seen that the sum of groove depth H14 and gap depth H9 is greaterthan the radial extension H6 of the annular member 6. By thisembodiment, a geometric overlap between the groove 6 and the toothing 9is achieved, so that the apertures 16 are formed with a definedgeometry. The geometry of the apertures 16 is substantially formed bythe geometry of the toothing 9. The plate carrier 2 is provided in theform of an outer plate carrier, wherein the first circumferential face 7constitutes an inner face of the annular member 6 and the secondcircumferential face 8 constitutes an outer face of the annular member6. A smallest radius R14 of the groove base 22 is smaller than a largesttooth base radius R12 of the teeth 9.

In the circumferential direction, the apertures 16 are delimited by twoopposed side faces 17, 17′ of two adjoining teeth 11. The teeth 11 eachcomprise a base region 18 with a substantially constant width B11 alongthe height. The expression “substantially constant” is intended tocomprise certain angular deviations of the tooth flanks 17, 17′ in thebase region 18 of up to five degrees. Accordingly, the tooth flanks 17,17′ circumferentially delimiting a tooth gap 16 extend substantiallyparallel relative to one another, so that a uniform width B16 of theapertures 16 results along the radial extension of the base region 18.This embodiment ensures that the apertures 16, in their radialdirection, comprise an at least substantially constant cross-sectionalface which is relatively large, thus achieving a good flow behaviour ofthe coolant from the inside of the outer plate carrier 2 towards theradial outside.

The ratio between the tooth thickness B11 in the base region and thewidth B16 of the apertures 16 preferably ranges between one and three,with the limits being included. This embodiment achieves a particularlyhigh strength of the plate carrier 2. However, it is understood thatother ratios are conceivable. The ratio between the tooth height H9 andthe radial thickness H23 of the annular web 23, which is formed betweenthe second circumferential face 8 and the tooth base line 15, preferablyranges between one and two, but deviating ratios are also generallyconceivable.

Further geometric details are shown in FIG. 7. The annular member 6comprises a greatest outer diameter D6. The annular groove 14 comprisesan axial length L14. Furthermore, the toothing 9 defines an effectiveportion with a length L19, which portion, in the mounted condition, ispositioned in the region of transition with the plate package. The ratiobetween the length L14 of the groove 14 and the effective axial lengthL19 of the toothing 9 can range between 0.2 and 0.6. This embodimentensures a good compromise between the achievable quantity ofthrough-flowing coolant and the strength of the plate carrier 2, but inprinciple other radios are also conceivable.

The ratio between the greatest outer diameter D6 of the annular member 6and the radial thickness H6 of the annular web preferably ranges between35 and 95, e.g., between 55 and 75. This embodiment, too, achieves goodstrength properties of the plate carrier 2.

Furthermore, it can be seen in FIG. 7 that the groove 14, if viewed in alongitudinal section through the plate carrier 2, comprises parallelside walls 20, 20′, as well as rounded transition regions 21, 21′towards the base 22 of the groove. The laterally axially adjoiningannular webs 23 of the annular member 6 each comprise a wall thicknessH23 which is smaller than the depth H14 of the groove. The annular webs23 can also be referred to as annular regions.

A process of producing the plate carrier 2 can comprise the followingprocess stages:

Producing an annular member 6 with a longitudinal axis A, a firstcircumferential face 7 with a toothing 9, and a second circumferentialface 8, as well as working in the groove 14 into the secondcircumferential face 8 of the annular member 6, wherein the groove 14,starting from the second circumferential face 8, is worked into theannular member 6 down to such a depth that radial apertures 16 areformed in the regions of intersection with the tooth gaps 12. Theannular member 6 can be pressed out of powder metal and subsequentlysolidified in a sintering process. The groove 14 is subsequently workedinto the sintered component, preferably by a chip-forming process, suchas turning or milling. Alternatively, the groove can also be worked intothe blank prior to the sintering process.

In the present embodiment the plate carrier 2 is provided in the form ofan outer plate carrier, i.e., the toothing 9 is provided in an innercircumferential face 8, whereas the groove 14 is provided in an outercircumferential face 7. For producing an inner plate carrier, the teethwould have to be on the outside and the groove on the inside. Anadvantage of said process is that one single production stage, i.e.,working in the groove 14, is sufficient for working several apertures 16simultaneously into the annular member 6. The process is thusparticularly efficient.

FIG. 8 shows a plate carrier 1 in a second embodiment which largelycorresponds to the embodiment according to FIGS. 1 to 7, so that as faras common features are concerned, reference is made to the abovedescription, with identical details or details corresponding to oneanother having been given the same reference numbers as in FIGS. 1 to 7.

A special feature of the embodiment according to FIG. 8 is that thereare provided two grooves 14, 14′ which are arranged in planes extendingradially relative to the axis of rotation A2 and are axially spacedrelative to one another. Both grooves 14, 14′ are continuously closed(annular grooves). By using two grooves 14, 14′, the through-flow areawhich is defined by the sum of all apertures 16, 16′ is increased.Overall, there is thus achieved an increased through-flow capacity forthe coolant from the inside of the outer plate carrier 2 to the radialoutside. When the clutch is opened, the coolant can quickly escapethrough the apertures 16,16′ into the outside, which leads to a definitereduction in the drag moment of the clutch.

In the present embodiment, the above-mentioned ratio between the lengthL16 of the apertures 16 and the effective axial length L19 of thetoothing 9 refers to the cumulated length of the apertures 16, 16′ in alongitudinal section through the plate carrier 2. This means for thepresent embodiment that the length of the apertures is composed of thelength L16 and the length L16′ (L16 _(tot)=L16 +L16′). It can be seenthat the width of the grooves L14, L14′, which define the length of theapertures 16, 16′, is of a same magnitude.

FIG. 9 shows a further embodiment of a plate carrier 2, which largelycorresponds to the embodiment according to FIG. 8, so that as far ascommon features are concerned, reference is made to the abovedescription, with identical details or details corresponding to oneanother having been given the same reference numbers as in FIG. 8.

A special feature of the embodiment according to FIG. 9 consists in thatthere are provided three grooves 14, 14′, 14″ which are arranged inplanes extending radially relative to the axis of rotation A2 and whichare axially spaced from one another. The three grooves 14, 14′, 14″ areprovided in the form of radially closed grooves (annular grooves). Byusing three grooves 14, 14′, 14″ the cumulated through-flow area can beeven further increased. When the clutch is open, the drag moment of theclutch can be thus reduced even further. The cumulative length L16tot ofthe apertures 16, 16′, 16″ in this case amounts to three times a lengthL16 (L16tot=L16+L16′+L16″).

FIGS. 10 and 11 show an annular member 6 for a plate carrier 2 in afurther embodiment which largely corresponds to the annular member 6 ofthe embodiment according to FIGS. 1 to 7, so that as far as commonfeatures are concerned, reference is made to the above description, withidentical details or details corresponding to one another having beengiven the same reference numbers as in FIGS. 1 to 7.

A special feature of the present embodiment consists in that severalgrooves 14 are arranged around the circumference, which are positionedin a common radial plane. A respective web 24 is formed between each twocircumferentially adjoining grooves 14. The webs 24 extend in thecircumferential direction at least around the circumferential region ofa tooth gap 12, and it is also conceivable to propose a largercircumferential extension which can comprise two or more tooth gaps. Anadvantage of the present embodiment with a plurality ofcircumferentially arranged grooves 14 with webs 24 located therebetweenrefers to a greater strength of the annular member 6 and of the platecarrier 2, respectively, and thus a higher torque capacity for themulti-plate clutch. In the present embodiment, there are provided threegrooves 14 with separating webs 24 therebetween, but it is understoodthat also a different number of two, four or more separating webs 24 canbe provided.

FIG. 12 shows a plate carrier 2 in a further embodiment which largelycorresponds to the embodiment according to FIGS. 1 to 7, so that as faras common features are concerned, reference is made to the abovedescription, with identical details or details corresponding to oneanother having been given the same reference numbers as in FIGS. 1 to 7.

In the embodiment according to FIG. 12 there are also provided severalgrooves 14, 14′, 14″, 14′″ (hereafter given the same reference number 14for simplicity). The grooves 14 have a main direction of extension inthe circumferential direction and comprise a smaller axial gradientcomponent. A gradient angle is enclosed between the grooves 14 and aradial plane extending perpendicularly relative to the longitudinal axisA, which gradient angle can amount to 0° to 10°. Overall, thisembodiment provides a helical shape of the grooves 14. The grooves 14are arranged such that each two adjoining grooves comprise a region ofoverlap 25 in the circumferential direction. Overall, with thisembodiment, too, there is ensured a larger total area of the apertures16 and thus a higher through-flow capacity for the coolant from theinner plate carrier 2 towards the outside.

In the present embodiment according to FIG. 12, four helical grooves 14are distributed around the circumference, but it is to be understoodthat a different number of two, three or more grooves 14 can also beused. In principle, because the grooves extend in the axial andcircumferential direction, this embodiment represents a combination ofthe embodiment according to FIG. 8 comprising several groovesdistributed in axial direction and the embodiment according to FIGS. 10and 11 comprising several circumferentially distributed grooves.

FIGS. 13 and 14 show an annular member 6 for a plate carrier 2 in afurther embodiment which largely corresponds to the embodiment accordingto FIGS. 1 to 7, so that as far as common features are concerned,reference is made to the above description, with identical details ordetails corresponding to one another having been given the samereference numbers as in FIGS. 1 to 7.

A special feature of the present embodiment according to FIGS. 13 and 14is that the annular member 6 is produced for example as a sheet metalpart or metal formed part. For this purpose, a sheet metal ring is firstproduced having a uniform wall thickness into which ring the toothing 9is worked by means of a forming operation. Because it is a sheet metalcomponent, the inner toothing 9 simultaneously forms an outer toothing9′. The inner toothing 9 comprises teeth 11 and tooth gaps 12, whichalternate along the circumference. The teeth 11 and tooth gaps 12 areprovided in the form of a cylindrical portions, with the inner face ofthe teeth 11 forming the inner circumferential face 7 and the outer faceof the arches 27 form the outer circumferential face 8. Thecircumferential extension of the teeth 11 approximately corresponds tothe circumferential extension of the gaps 12 formed between two teeth.Subsequently, die groove 14 is worked into the annular member 6comprising the formed-in toothing 9, which operation can take place bymaking use of a chip-forming process such as turning or milling. In thepresent embodiment, too, the depth H14 of the groove 14 is worked indown to a depth where there are produced apertures 16 towards the toothgaps 12. This is achieved in that the sum of the groove depth H14 andthe tooth height H9 is greater than the radial extension H6 between theinner circumferential face 7 and the outer circumferential face 8.Alternatively, it is also conceivable to produce the toothing geometryaccording to FIGS. 13 and 14 by a powder metal process.

An advantage of the present embodiment consists in that, due to anoptimised geometry and the improved production process, it comprises asmall wall thickness and thus a lower weight. The present embodiment canalso be used as an inner plate carrier, optionally with the geometricdimensions being adapted to the technical requirements. In that case,the inner plates would engage the outer toothing 9′ for transmittingtorque.

FIGS. 15 to 17 which will be described jointly below show a platecarrier 52 in a further embodiment which largely corresponds to theembodiment according to FIGS. 1 to 7 to the description of whichreference is hereby made, with identical components or componentscorresponding to one another having been provided with reference numbersincreased by the FIG. 50.

The plate carrier 52 according to the present embodiment is provided inthe form of an inner plate carrier and comprises a hub portion 53 withhub teeth 54 which, for torque transmitting purposes, can beform-fittingly engaged by a driveshaft (not illustrated). The hubportion 53 is adjoined by a flange portion 55 from which there extendsthe annular potion 56 in the axial direction. The annular portion 56which can also be referred to as the annular member comprises a firstcircumferential face 57 which is provided in the form of an outer face,and a second circumferential face 58 which is provided in the form of aninner face. As the present embodiment constitutes an inner platecarrier, the toothing 59 is formed in the outer circumferential face 57,whereas the groove 64 is provided in the inner circumferential face 58.It can be seen in FIGS. 15 and 16 that two grooves 64, 64′ extendparallel relative to one another in planes extending radially relativeto the axis of rotation A52.

The toothing 59 provided in the form of outer teeth, can be engaged in arotationally fixed and axially movable way by inner plates (notillustrated) having corresponding inner teeth, for torque transmittingpurposes. The toothing 59 comprises circumferentially alternating teeth61 and tooth gaps 62 which extend in an axial direction. The toothing 59is provided in the form of a straight or spur toothing. The teeth 61comprise a tooth head line 63, which forms the outer firstcircumferential face 57, and a tooth base line 65. A greatest radius R64of the groove base 72 is greater than a smallest tooth base radius R59of the teeth 61.

Two grooves 64, 64′ which are arranged parallel relative to one anotherand which extend in the circumferential direction are worked into theinner second circumferential face 57. The grooves 64, 64′ arecontinuously closed and can therefore also be referred to as annulargrooves. The annular grooves extend in planes which extendperpendicularly relative to the longitudinal axis A52. The grooves 64,64′ extend from the inner circumferential face 58 radially outwardly asfar as and beyond the tooth base line 65 of the toothing 59, so that—inthe region of the circumferential extension of the grooves 64,64′—radial apertures 66, 66′ are formed between each two teeth 61.

Starting from the inner circumferential face 58, the grooves 64, 64′comprise a groove depth H64. Starting from the outer circumferentialface 57, the tooth gaps 52 comprise a gap depth H59 which corresponds tothe tooth height. Furthermore, between the outer circumferential face 57and the inner circumferential face 58, the annular member 56 comprises aradial extension H56 which can also be referred to as thickness. It alsoapplies to the present embodiment that the sum of groove depth H64 andthe gap depth H9 is greater than the radial extension H56 of the annularmember 56. Thus, it is possible to achieve a geometric overlap betweenthe grooves 64, 64′ and the toothing 59, so that the apertures 66, 66′are formed with a defined geometry.

Apart from that, the plate carrier 52 substantially corresponds to theabove embodiments to the description of which reference is hereby made.It is understood that, more particularly, in respect of the number anddesign of the grooves 64, 64′, modifications of the plate carrier 52provided in the form of inner plate carrier are conceivable, as shown inFIGS. 1 to 14. More particularly, it is possible to use only one groove,or a plurality of grooves in a radial plane, or one or several helicalgrooves.

A multi-plate clutch can be composed of an outer plate carrier 2according to FIGS. 1 to 7 and an inner plate carrier 52 according toFIGS. 15 to 17. However, it is understood that the outer plate carrieraccording to FIGS. 1 to 7 could also be combined with a different innerplate carrier, also with an inner plate carrier without apertures orwith other types of apertures. Accordingly, it is understood that theinner plate carrier could be combined with a different outer platecarrier.

Overall, a multi-plate clutch with an outer plate carrier according tothe embodiment according to FIGS. 1 to 14 and/or an inner plate carrieraccording to FIGS. 15 to 17 offer/offers an advantage of having goodcoolant through-flow conditions combined with a high strength value. Forreducing the drag moment of the clutch it is particularly advantageousif the outer plate carrier is designed in accordance with the disclosedembodiment, which means that with an open clutch, the coolant can escapeparticularly quickly from the plate package, which, in turn, leads to areduction in friction losses.

1.-17. (canceled)
 18. A multi-plate clutch comprising: an outer platecarrier to which outer plates are connected in a rotationally fixed andaxially movable way; an inner plate carrier to which inner plates areconnected in a rotationally fixed and axially movable way; wherein theouter plates and the inner plates form a plate package; wherein theouter plate carrier and the inner plate carrier are rotatable relativeto one another around an axis of rotation; wherein, by introducing anaxial force, the outer plates and the inner plates are brought intofrictional contact with one another to selectively transmit torquebetween the outer plate carrier and the inner plate carrier; and whereinat least one of the outer and of the inner plate carrier comprises: anannular member with a first circumferential face and a secondcircumferential face; a toothing in the first circumferential face ofthe annular member, said toothing comprising teeth and tooth gaps whichare circumferentially distributed; at least one groove in the secondcircumferential face of the annular member, wherein the at least onegroove extends in circumferential direction of the annular member and iscontinuously closed, wherein the at least one groove is arranged withinan effective axial length of the toothing along which length the platepackage extends; wherein the at least one groove and the toothingintersect one another such that, along a circumferential extension ofthe at least one groove, a plurality of radial apertures are formed inthe annular member in regions of intersection between the at least onegroove and at least some of the tooth gaps of the toothing.
 19. Themulti-plate clutch according to claim 18, wherein, starting from thesecond circumferential face, the at least one groove comprises a groovedepth, and wherein, starting from the first circumferential face, thetooth gaps comprise a tooth gap depth in a cross-section axiallyadjacent to the groove, wherein a sum of the groove depth and the toothgap depth is greater than a radial thickness between the firstcircumferential face and the second circumferential face.
 20. Themulti-plate clutch according to claim 18, wherein in a cross-sectionalplane along the at least one groove, a tooth of the toothing comprise agreatest tooth thickness, and wherein the radial apertures between twoteeth comprise a greatest width, wherein the greatest tooth thickness ofa tooth amounts to at least one of at least the greatest width of aradial aperture and at most three times the greatest width of the radialaperture.
 21. The multi-plate clutch according to claim 18, wherein theannular member comprises an annular web formed between the secondcircumferential face and a tooth root line of the toothing, whichannular web comprises a radial thickness, wherein, in a cross-sectionalplane through said annular web, the teeth of the toothing comprise agreatest tooth height, and wherein the greatest tooth height amounts toat least one of at least the radial thickness of the annular web and atmost double the radial thickness of the annular web.
 22. The multi-plateclutch according to claim 18, wherein the annular member comprises agreatest outer diameter and an annular web formed between the secondcircumferential face and a tooth root line of the toothing, wherein theannular web comprises a radial thickness, wherein a greatest outerdiameter of the annular member amounts to at least one of at least 35times the radial thickness of the annular web and at most 95 times theradial thickness of the annular web.
 23. The multi-plate clutchaccording to claim 18, wherein, in a longitudinal sectional planethrough the at least one plate carrier, there is provided at least oneaperture, wherein a sum of the at least one aperture existing in thelongitudinal sectional plane defines a cumulated length, and wherein thecumulated length of the at least one aperture amounts to at least one ofat least 0.2 times the effective axial length of the toothing and atmost 0.6 times the effective axial length of the toothing.
 24. Themulti-plate clutch according to claim 23, wherein the radial aperturesare each laterally delimited by two circumferentially opposed side facesof two adjoining teeth, wherein the two opposed side faces extend atleast substantially parallel relative to one another.
 25. Themulti-plate clutch according to claim 18, wherein the firstcircumferential face constitutes an inner face of the annular member andthe second circumferential face constitutes an outer face of the annularmember, wherein a smallest radius of a groove base of the at least onegroove is smaller than a tooth root radius of the toothing.
 26. Themulti-plate clutch according to claim 18, wherein the firstcircumferential face constitutes an outer face of the annular member andthe second circumferential face constitutes an inner face of the annularmember, wherein a greatest radius of a groove base of the at least onegroove is greater than a tooth root radius of the toothing.
 27. Themulti-plate clutch according to claim 18, wherein a plurality of groovesis provided, wherein the grooves are axially spaced relative to oneanother, wherein each of the plurality of grooves forms a row ofapertures in a region of overlap with the tooth gaps.
 28. Themulti-plate clutch according to claim 18, wherein the at least onegroove comprises rounded recesses in a cross-sectional view through theat least one groove.
 29. The multi-plate clutch according to claim 18,wherein the annular member is a sintered component which is produced outof powder metal in a pressing and sintering operation.
 30. Themulti-plate clutch according to claim 18, wherein the at least onegroove is worked into the annular member by a turning operation.